Jahangirnagar University Journal of Electronics and Computer Science

Cross-Layer Analytical Model for Cognitive Radio Network under Engset and M/G/1/m Traffic

2023-03-27T15:24:59+06:00

This paper deals with the performance of secondary users (SUs) based on dynamic scheduling of users based on cross-layer analytical model. Under this scheme the number secondary users in a network are kept limited to discourage malicious users hence Engset’s traffic model is more appropriate than the Erlang’s model of previous literature. We also incorporate M/G/1(m) traffic model, applicable for ATM/TCP-IP traffic, in cognitive radio network under crosslayer analytical model. Finally, impact of spectrum sensing period and probability of false alarm on blocking probability of secondary users are analyzed.

Impact of Geometry and Feed Point on Radiation Pattern of a Patch Antenna and Its Linear Array as a Substitute of Multi-hop Link

2023-03-27T15:36:07+06:00

Rao-Wilton-Glisson (RWG) edge elements are widely used to determine the performance of an antenna specially the distribution of elemental dipole on the antenna surface, surface current distribution, profile of input impedance and radiation pattern. In this paper the impact of geometry and position of feed point of a patch antenna is analyzed in terms of variation of input impedance against frequency to get the bandwidth of the antenna and radiation pattern on both two dimensional surface and three dimensional space. Finally an array of such antenna is placed on a line to observe the end fire and broad side radiation pattern to get intense and heavily directed beam, can be used as substitute of multi hop ad-hoc link.

Recovery of Grayscale Image from Its Halftoned Version Using Smooth Window Function

2023-03-27T15:42:00+06:00

In a grayscale image of 256 levels, it is indistinguishable between intensity levels hence it is called continuous tone image. In a binary image the mark and space are
distinguishable but sharp change in intensity level makes the quality of the image very poor. The half tone image is also a binary image but varying the size of pixels and its density improves the quality of the image. The halftone image here can be considered as the truncated normalized version of continuous tone image. Based on this concept smoothing the transition of half tone image by convolutional operator with a smooth window function can recover the continuous tone image. Finally noise
grains are eliminated applying DWT (Discrete Wavelet Transform), gives the much closed perception of grayscale image. Although the similar concept is applied in blurring of a continuous tone image but in this paper similar concept is applied to half-tone operation to avoid the complexity of RI (Recursive Inverse) and RWI (Regularized Wiener Inversion) algorithm.

Performance Evaluation of Cognitive Radio Network under Limited User Traffic

2023-03-27T15:46:13+06:00

Now-a-days optimum utilization of spectrum of a wireless network is performed based on Cognitive Radio (CR) system. In this paper performance of such network is evaluated using two dimensional Markov chain under limited user case. The closed form expression for throughput and call blocking probability is derived in terms of traffic parameters. The impact of number of channel, number of primary and secondary user on throughput and call blocking probability is analyzed.